Abstract: Liquid-liquid extractive separation in batches was a rapid and accurate method. It had many advantages, and could be extensively used in the analytical laboratory. In order to separate and determine the drug mixture, a large difference in distribution percentage (DP) was demanded. This study was based on the determination of DP of drugs. From our experimental results we found preliminarily some rules.Samples were mainly tertiary amines as well as some quaternary ammonium salts and degradation acids. First, we tested the DP of drugs in 1N HCl with fourteen organic solvents. A regular relationship was obtained, i e the DP of tertiary amines depended upon the dielectric constant in two kinds of solvents, namely, halogenated hydrocarbons and non-halogenated organic solvents. Generally, the DP became large with increasing dielectric constant. And further, we selected five kinds of solvents, namely, alkane, ether, ketone, alcohol and halogenated hydrocarbon. With these solvents, the DP of drugs at different pH was tested. By these tests it was found that halogenated hydrocarbon was the best. In an acidic solution, the difference in DP of tertiary amines in halogenated hydrocarbons was the largest, so that these solvents might be used for the separation of tertiary amines. Alcohols were the next preferable solvent, with which some tertiary amines could also be separated.In an acidic solution, the range of difference in DP of amine drugs for these five kinds of solvent changed according to their dielectric constants. The patterns of DP curves in halogenated hydrocarbons containing active hydrogen atoms resembled each other, but the curves shifted to higher pH side with increasing dielec-tric constant.This study indicated that DP of tertiary amines depended upon the pH of the aqueous solution. Thus, with the aid of the difference DP at the selected pH, the drug mixture could be separated with halogenated hydrocarbons containing active hydrogen atom.This separation method combined with spectrophotometry, colorimetry of acid dye extraction or colorimetry of color reaction had been used for the separation and determination of seven drug mixtures. The largest coefficient of variance of determination was ±1.6%.In addition, it was found that DP increased with increasing temperature and decreased with decreasing temperature. Rf values obtained by paper partition chromatography were similar to DP (R Value), thus DP could be predicted by paper partition chromatography.This study also indicated that even in an acidic solution, organic solvents (including halogenated hydrocarbons and alcohols containing an active hydrogen atom as well as ketones containing an electro-negative atom) could extract the amines.